VICTORIA _ British Columbia's New Democrats and Greens signed a four-year political manifesto Tuesday with a long list of ambitions to run the province, including a new voting system and a ban on corporate and union donations.

It also seeks to stop the Kinder Morgan's $7.4 billion pipeline expansion project and require further reviews of the $8.8 billion Site C hydroelectric dam.

But the unprecedented political agreement for an NDP minority government will have to wait until Premier Christy Clark recalls the legislature for what she said would likely be the end of her government in a confidence vote.

NDP Leader John Horgan and Green Leader Andrew Weaver didn't take issue with Clark's decision to lose in a house vote, but want her to move quickly.

Identify opportunities and empower your strategic decision making with the Daily Oil Bulletin.

"I'm hopeful that if Ms. Clark does want to go through with that precedent, that she does so in a timely manner," Horgan said after signing the 10-page agreement during a ceremony with Weaver at the legislature.

The agreement would see the legislature recalled within one month of the swearing in of an NDP government and its first order of business would be legislation to hold a referendum next year on proportional representation.

"We're going to work together on this," said Weaver. "The goal is to have a very clear question after an extensive consultative process that John and I and our various teams campaign on as opposed to against."

The two parties also agreed to introduce legislation to ban corporate and union donations to political parties, as well as contributions from non-residents of B.C. after fundraising became a major issue in this month's provincial election campaign.

The parties said they would use "every tool available" to stop the expansion of Kinder Morgan's Trans Mountain pipeline, and would refer the Site C dam, which is already under construction, to the B.C. Utilities Commission to determine its economic viability.

The likelihood of a renewed debate on the Trans Mountain pipeline drew reaction from outside the province even before Horgan said the parties have a responsibility to "defend" the coastline of British Columbia and stop the pipeline, which would increase tanker traffic seven-fold off the west coast.

Both Prime Minister Justin Trudeau and Alberta Premier Rachel Notley defended the pipeline expansion, saying it is in the country's best interests.

"And mark my words: that pipeline will be built," Notley said.

Weaver said comments in support of the pipeline are misguided, likening them to Clark's promises in the 2013 election campaign to the potential prosperity of a liquefied natural gas industry.

"The challenge here is to demonstrate to British Columbians, as we are today, that people from different political persuasions can come together in the interest of British Columbians so people don't fear minority governments, in fact, they embrace them," Horgan said.

Although Clark appeared resigned to the outcome of a confidence motion, she said she is not ready to walk away from office before recalling the legislature to see if she can get support to continue governing.

She said it would be up to the lieutenant-governor to decide whether the NDP can take power or call a new election if the Liberals are defeated.

"What's most important is this basic principle, that if there is going to be a transfer of power in this province, and it certainly seems like there will be, it shouldn't be done behind closed doors," she told a news conference in Vancouver.

Clark said if her government loses a confidence vote, she would be willing to serve as Opposition leader.

She said she plans to bring the house back in June and made the decision to test the will of the legislature after consulting constitutional experts.

The Liberals have been in power for 16 years. They took 43 seats in the election, one short of a majority, compared with 41 for the NDP and three for the Greens, leaving them with the balance of power for the first time in Canadian history.

The Greens went into negotiations with the other two parties shortly after the May 9 election making three key demands: getting official party status in the legislature, an electoral system based on proportional representation and political fundraising reform.

The Greens and NDP have supported a system of proportional representation that accounts for the number of seats each party gets in the legislature based on their percentage of the popular vote.

Two previous referendums on proportional representation have failed in B.C.

Under the terms of the NDP-Green agreement, the next referendum would take place when municipal elections are held in the fall of the 2018.